KNbO_3陶瓷的半导化及PTC效应

PTC Effect in KNbO_3 Semiconducting Ceramics

采用添加钾锗玻璃和掺ＭｏＯ＿３的方法，制备了ＫＮｂＯ＿３半导瓷。在此基础上，对ＫＮｂＯ＿３半导瓷样品进行了电学性能的测试以及样品断面形貌的扫描电镜观察和分析，结果表明，两种方法制备的ＫＮｂＯ＿３半导瓷样品都在铌酸钾晶体的两个相变点附近出现了ＰＴＣ电阻异常：一个在正交铁电相──四方铁电相转变处：另一个在四方铁电相──立方顺电相转变处。而掺ＭｏＯ＿３制备的半导瓷具有较小室温电阻率及较大的电阻率反常幅度（ＦＥ－ＦＥ处），且两种方法制备的半导瓷的导电类型有所差导。

spccimens of semiconducting ceramics KNbO_3 have been. preparedby doping with K_2O-GeO_2 glasses, and by doping with MoO_3. The dielectric propertyand conductivity measurements have been made as a function of temperature, Themicrostructures have been examined by the scanning electron microscope. The experimen-tal results show that two PTC anomalies in the vicinity of the orthorhombic-tetragonal andthe tetragonal-cubic transition temperatures of KNbO_3 crystal. Smaller resistivity andlarger anomaly in resistivity(FE-FE) are observed in the samples with addition ofMoO_3. The conduction mechanism in semiconductive ceramics KNbO_3 is discussedfinally.